Bunuel wrote:
An airplane took off from airport P and later landed at airport R at the same time that another airplane landed at airport R, completing its flight from airport Q. If both flights were nonstop flights, which airplane flew at the faster average speed?
(1) The first plane took off a half hour before the second plane.
(2) The distance from P to R is greater than the distance from Q to R.
Let distance between P and R be d1 and distance between Q and R be d2. Let the time taken by first plane for its PR journey be t1 and let the time taken by second plane for its QR journey be t2.
So average speed of first plane = d1/t1
and average speed of second plane = d2/t2.
We have to compare these two speeds.
(1) This tells us that first plane travelled for half an hour more than second plane. So we have t1 = t2 + 0.5
Now speed of first plane = d1 / (t2 + 0.5)
and speed of second plane = d2/t2
But we cannot compare them without having any idea of d1 and d2.
Not sufficient.
(2) d1 > d2. But without any idea of t1 and t2 we cannot compare.
Not sufficient.
Combining the two statements, speed of first plane = d1 / (t2 + 0.5) and speed of second plane = d2/t2. We also know that numerator of first one d1 is greater than numerator of second one, d2. Also denominator of first one is greater than denominator of second one. Both numerator and denominator are larger, but we dont know by what percentage or by what fraction. So we cannot compare.
Not Sufficient.
Hence
E answer